和泉正宗(松冈祯丞 配音)是一名专注于创作轻小说的作家,曾经获得过新人奖,并就此踏上了写作的道路。不久之前,正宗开始了和没有血缘关系的妹妹和泉纱雾(藤田茜 配音)一起的同居生活,哪知道虽然住在同一屋檐下,但正宗几乎没有在家里看到过纱雾,因为纱雾是一个只待在自己房间里绝对不会出来的超级宅女。 负责给正宗的小说画插图的是一位名叫“情色漫画老师”的插画家,其画技之精湛令正宗深深折服,然而,情色漫画老师未曾有过以其真身示人之时,对于他隐藏在网络背后的真实面目,正宗有着诸多的猜测。然而,让正宗没有想到的是,这位插画家的真身,竟然就是妹妹纱雾!The "new sibling romantic comedy" revolves around Masamune Izumi, a light novel author in high school. Masamune's little sister is Sagiri, a shut-in girl who hasn't left her room for an entire year. She even forces her brother to make and bring her meals when she stomps the floor. Masamune wants his sister to leave her room, because the two of them are each other's only family. Masamune's novel illustrator, pen name "Eromanga," draws extremely perverted drawings, and is very reliable. Masamune had never met his illustrator, and figured he was just a disgusting, perverted otaku. However, the truth is revealed - that his "Eromanga-sensei" is his own younger sister. To add to the chaos that erupts between the siblings, a beautiful, female, best-selling shoujo manga creator becomes their rival.